Add initial .mailmap file.

Not perfect yet, but it covers all committers with 10 or more commits.  I
didn't go looking below that threshold.

.mailmap

+Stefan Behnel <stefan_ml@behnel.de> Stefan Behnel <scoder@users.berlios.de>
+Stefan Behnel <stefan_ml@behnel.de> scoder <stefan_ml@behnel.de>
+Stefan Behnel <stefan_ml@behnel.de> Stefan Behnel <stb@skoobe.de>
+Robert Bradshaw <robertwb@gmail.com> Robert Bradshaw <robertwb@math.washington.edu>
+Robert Bradshaw <robertwb@gmail.com> Robert Bradshaw <robertwb@google.com>
+Robert Bradshaw <robertwb@gmail.com> robertwb <robertwb@gmail.com>
+Robert Bradshaw <robertwb@gmail.com> Robert Bradshaw <robertwb@robertwb-macbookpro.local>
+Mark Florisson <markflorisson88@gmail.com> Mark <markflorisson88@gmail.com>
+Mark Florisson <markflorisson88@gmail.com> Mark Florisson <eggy.nospam@gmail.com>
+Lars Buitinck <larsmans@gmail.com> Lars Buitinck <L.J.Buitinck@uva.nl>
+Danilo Freitas <dsurviver@gmail.com> DaniloFreitas <dsurviver@gmail.com>
+Danilo Freitas <dsurviver@gmail.com> daniloaf@daniloaf-PC <none@none>
+Danilo Freitas <dsurviver@gmail.com> daniloaf <none@none>
+Lisandro Dalcin <dalcinl@gmail.com> dalcinl <none@none>
+Christoph Gohlke <cgohlke@uci.edu> cgohlke <cgohlke@uci.edu>